Serological Evidence of SARS-CoV-2 Exposure in Domestic Dogs and Cats, Thailand: Detection of SARS-CoV-2 Omicron Variant in Dogs Living in COVID-19-Positive Households

SARS-CoV-2 causes the coronavirus disease 2019 (COVID-19) pandemic. Cross-species transmission of SARS-CoV-2 from humans to domestic animals has been reported. In this study, we conducted a serological survey and molecular investigation of SARS-CoV-2 infection in domestic dogs and cats in Bangkok and the vicinities from January 2021 to August 2022. A total of 2,664 serum samples were examined for antibodies against SARS-CoV-2 using nucleocapsid protein-based ELISA (NP-ELISA). Our result showed 2.28% (33/1,446) seropositivity in dogs and 1.81% (22/1,218) in cats. The positive NP-ELISA serum samples were confirmed using a surrogate virus neutralization test (sVNT). Of 55 seropositive samples by NP-ELISA, two dogs and 19 cats were confirmed seropositive by sVNT. Our result supported the serological evidence of SARS-CoV-2 exposure in domestic dogs and cats. We also investigated SARS-CoV-2 infection by real-time RT-PCR in 156 domestic dogs and cats in COVID-19-positive households. Our result showed active SARS-CoV-2 infection in a dog living with COVID-19 positive owner. Genetic and phylogenetic analysis of the SARS-CoV-2 from the dog and its owner confirmed the SARS-CoV-2 variant Omicron BA.2. It is the first report of SARS-CoV-2 Omicron variant in pet living in COVID-19-positive household in Thailand.